Advanced antenna systems may be used to enhance performance of wireless communications systems in uplink (UL) as well as in downlink (DL). One way to accomplish this performance enhancement is to use beamforming. Beamforming enables a radiation pattern of the advanced antenna system to be controlled by transmitting a signal from a plurality of antenna elements using a gain and phase specific for the individual antenna elements. In this way, radiation patterns with different pointing directions and beam widths in both elevation and azimuth directions may be created.
In wireless communications systems such as High Speed Packet Access (HSPA) and Long Term Evolution (LTE), common reference signals are transmitted (Common Pilot Channel, CPICH, and Cell Specific Reference Signal, CRS, respectively). These signals are measured by terminals (denoted user equipment, UE, in case of LTE) for instance for selecting a network node to communicate with, and as demodulation reference signals for data to be received by terminals served by the network node. Often, the area where a specific cell specific reference signal is received with highest power (as compared to cell specific reference signals transmitted from other network nodes) is referred to as a cell, and changing of beamforming patterns of the cell specific reference signal may therefore be referred to as “cell shaping”.
This modification of cell uptake areas, i.e. the cell shaping, may for instance be done in order to distribute terminals between the cells more evenly (load balancing in the network nodes), which in turn may optimize coverage and/or capacity in the wireless communications system. The cell shaping in a wireless communications system may be automatically adjusted by employing a reconfigurable antenna system and a self-organizing network (RAS-SON) algorithm that adjusts the cell shapes based on some given network measurements and target performance metric.
Blind handover is an existing feature in which the network node, e.g. an evolved NodeB (eNodeB, or also denoted eNB) in case of LTE, may initiate a handover procedure for a terminal without doing conventional measurement configuration and without considering measurement reports. This feature may be beneficial when a fast handover is needed and candidate cell measurements are unavailable, or would impose an unwanted delay. Using the blind handover in such case removes the time and signaling needed to conduct handover measurements, hence giving the desired fast handover.